Sponsored by AUS
By Jim Rickner
As a biomedical engineer we may be asked to perform first call on an ultrasound system. Many times, this means troubleshooting a system that you have no background working on or formal training to fall back on. To help guide you, we have attempted to simplify how ultrasounds work, define what probes are used for different studies, and cover some common failures to help. With that in mind, let’s get started.
Ultrasound refers to sound at frequencies above the range of human hearing. In diagnostic imaging, it typically uses frequencies between 1 MHz and 20 MHz. By using different frequencies in this range, we can look at different structures in the human body. Lower frequency offers more penetration but less resolution. Higher frequencies have high resolution but low penetration. This is a critical principle in ultrasound.
The ultrasound system itself can be divided into three subsystems commonly called the Front End, Back End and Power. By understanding the primary purpose of each subsystem, you can more easily troubleshoot issues with the system. So, let’s break it down.
Let’s begin with the Front End. This is where the sound waves are transmitted into the human body and echoes from tissue structures are acquired. This is normally the source of image artifacts that radiate from the probe throughout the image.
The Back End is the computer that runs on an operating system (usually Windows) and applications software. This is where the acquired ultrasound data is converted into a format that can be displayed on the monitor. The Back End is responsible for the video and audio signals for the ultrasound. If the software is corrupted or the computer has a failure the ultrasound system will not boot into imaging.
The Power supply sub-system provides the voltages needed to run the computer and electronics throughout the system. It is usually divided into two categories, low voltage and high voltage. Low voltage, also referred to as logic voltage operates the computer and associated circuit boards while the high voltage supplies the transmit voltage needed to excite the crystals in the probe which then vibrates and generates the sound waves into the human body. Power sub-system failures can cause a wide variety of symptoms throughout the ultrasound system.
A critical portion of the Front End that we haven’t spoken about yet are the probes. Also known as transducers, they are key to system image quality and can be easily damaged. There are many different types of probes, and each have different applications. We are going to stick with the three most common types of probes, the linear, curved, and phased array.
The linear probe is usually used for body structures close to the surface such as thyroid, vascular, small parts, and breast imaging studies. They are usually a mid-to-high frequency probe offering better image quality.
The curved probe is an abdominal probe commonly used in OB/GYN studies. It is normally a low-to-mid frequency probe that offers more penetration.
The last probe we discuss is the phased array probe. These probes are normally used in cardiac exams but can also be used in some abdominal studies. They are low frequency probes that offer high penetration and a unique image area that looks like a slice of pie.
Although each type of probe has different uses, they are all extremely fragile and easily damaged. As a high failure item on ultrasounds, it is important to stay vigilant. Once a probe is suspected of causing image quality issues, a simple troubleshooting technique is trying multiple probes in multiple ports. This will allow you to quickly determine if the problem is probe or system related.
A portion of the Back End sub-system that is prone to failure is the software. Whether it is caused by a defective hard drive or gets corrupted, software is a high failure component of ultrasounds. Being proactive is one of your best defenses against software failure. Make sure you have a copy of system software prior to needing it. Make a system backup disk and capture the system’s vital product data such as software level, installed options and network information. Armed with these items, you can oftentimes quickly reload and restore the system to full operation.
Finally, make sure you thoroughly understand the issue the technologist is describing. If you are unclear about what they are describing, have them show you. This is a critical step in efficient troubleshooting. Once you are confident that you know the issues the technologist is experiencing, you can divide and conquer by asking yourself, are these issues caused by the Front End, Back End or Power?
Although this is far from an all-inclusive introduction to servicing diagnostic ultrasound, these guidelines can provide a simple troubleshooting path that is easy to follow and efficient. So, get out there and put this knowledge to good use with confidence! •
Jim Rickner is the director of service and training at Advanced Ultrasound Systems, an ISO 13485:2016 company.
